It is conventional practice to make up a perforating gun having a plurality of chambers arranged one above another with each chamber containing an explosive charge, usually in the form of one or more shaped charge units. The explosive charges are commonly fired successively from bottom to top. It is necessary that the ignition of the explosive charge in one chamber will not adversely affect the ignition of those in other chambers. Consequently, it is necessary that the explosive charge of a particular chamber be effectively isolated and sealed relative to the next adjacent chamber.
Prior art practices are exemplified by my U.S. Pat. No. 3,768,408; B. J. Boop, et al, U.S. Pat. Nos. 3,528,511 and 3,528,512; and my U.S. application Ser. No. 661,796, filed Feb. 26, 1976, now U.S. Pat. 4,089,381, which is assigned to the assignee of the present invention.
In the practice ememplified by the Boop, et al, patents, adjacent chambers are isolated by a partition or sub, with ignition wires being passed through a passageway in the sub to the chamber or chambers below. Each passageway is provided a seat at its lower end portion, with a sealing projectile disposed adjacent the seat. The explosive charges in the chambers are fired successively from bottom to top. When the explosive charge of a chamber is fired, the detonating of the explosive charge drives the respective sealing projectile into its seat and the passageway to sever the ignition wires and form a seal, so that the chamber just fired is isolated both electrically and physically from the chambers above.
It has been found that sealing projectiles of the type disclosed by the Boop, et al, patents, above mentioned, are subject to significant deficiencies. The sealing projectile of the Boop, et al, patents has a conical shaped nose portion and because of the ignition wires, the sealing projectile is not driven onto its seat in a symmetrical manner, and the conical surface tends to be gouged by contact with the seat. In addition, the ignition wires tend to be subjected to a pinching or squeezing action instead of being cut cleanly, and the ignition wire severing action tends not to be completed prior to the beginning of the sealing action. As a consequence, an effective seal is not always attained.
It is, accordingly, an object of this invention to provide an improved sealing projectile that will consistently attain an effective seal.
Another object of the invention is to provide an improved sealing projectile which will be driven onto its seat in a symmetrical manner.
Another object of the invention is to provide an improved sealing projectile which will effect efficient severing of ignition wires.
Another object of the invention is to provide an improved sealing projectile such that the ignition wires will be severed prior to the beginning of the sealing action.
For a further understanding of the invention and further objectives, features, and advantages thereof, reference may now be had to the following description, taken in conjunction with the accompanying drawings.